i can get great
hi res laced/lo res laced full screen perfect
but only half screen hi res/lo res non laced
using 1280x1024 screen mode on a dell 1280x1024 vga monitor

If you mean PAL non-interlaced, then that's 256 lines and with scanlines it can be stretched to 512 lines, which is why it can't be more than half screen. You need to choose a lower output resolution if you want it to be full screen.